This application is directed to transmission assemblies, and more particularly to gas risers used in transmitting natural gas from a buried underground gas line to a home or business.
U.S. Pat. No. 5,590,914 is commonly owned by the assignee of the present application and the details of that patent are incorporated herein by reference. It generally illustrates a gas riser assembly of the type to which the subject invention pertains where natural gas is supplied from a main, through a buried service line, and eventually to the riser assembly. The riser assembly extends from an underground connection with the service line, through an elbow region, to a vertically disposed pipe that communicates with a manifold of an above-ground gas meter.
The gas riser assembly is either factory-assembled or intended for assembly in the field. In either case, the gas riser assembly includes a double-walled conduit comprising an inner, plastic tube or casing received inside a rigid, outer casing. The inner casing defines the fluid passage for the gas as it is transported from the main to the meter. Spacers may be provided at selected axial locations along the length of the assembly, if desired. The riser assembly is connected to the manifold in a fluid tight manner so that a sealed passageway is provided from the underground connection to the manifold.
Strength of the riser is an important consideration. It must be strong enough to support the weight load of the residential piping system, while maintaining a sealed relationship with the manifold.
It is also desirable to use corrosion-free materials in riser assembly since the outer casing, which is typically made of steel, is otherwise subject to corrosive attack. For this reason, the outer casing is usually treated, i.e., coated. The coating operation adds to the overall cost of the assembly.
In prior arrangements, the end of the riser that connects with the manifold is a rigid structure. When the riser assembly is connected to the manifold, joint stress can build up in the assembly. Moreover, disassembly required the loss of a gas seal of the tensile grip on the internal tube of the riser assembly. Additionally, the designs were either intended for factory assembly or field assembly, as opposed to being modular in design to allow flexibility.
Corrosion resistance is also a concern. It is also preferred that the assembly be electrically isolated from ground contact, and strong enough to support the weight load of the residential piping assembly. Known assemblies, though, often require some type of corrosion protection or an auxiliary support device, i.e., a bracket assembly, to achieve these objectives.
Thus, there is a desire for a new and improved riser assembly that achieves these various objectives and results in an extended service life.
The present invention provides a riser assembly that overcomes the noted drawbacks in a simple, economical manner.
According to the invention, there is provided a riser assembly having an adapter that connects to a manifold at one end, and has an opening at an opposite end adapted to receive the double walled conduits or casings therein. An inner casing is held in the adapter by a gripping assembly. An outer casing concentrically surrounds the inner casing and is held in the adapter by a mounting assembly. The mounting assembly prevents pullout of the outer casing from the adapter and allows the outer casing to freely rotate relative to the adapter.
According to another aspect of the invention, the outer casing is a plastic material that provides corrosion resistant and dielectric properties.
According to still another aspect of the invention, the outer casing is defined by a metal tube coated in plastic.
According to yet another aspect of the invention, the mounting assembly includes a toothed collet.
A principal benefit of the present invention is the ability to rotate the outer casing relative to the adapter for ease of assembly and disassembly.
Yet another benefit of the present invention resides in the modular design that allows factory or in-field assembly of the gas riser.
Yet another advantage of the invention is found in the corrosion resistant, electrically isolated assembly that is able to meet the demands of piping systems.
Still other advantages and benefits of the present invention will become more apparent to one skilled in the art upon a reading and understanding of the following specification.